1. Statement of the Technical Field
The present invention relates to the cache management and more particularly to providing differentiated service in a caching system.
2. Description of the Related Art
The modern global network can be viewed as a complex interweaving of multiple network technologies, server platforms, client capabilities and application requirements. The vast majority of network technologies handle device requests indiscriminately. That is, regardless of the identity of the requester or the type of request, each device request can be processed with equal priority. Given the exponential increase in network traffic across the Internet, however, more recent network-oriented computing devices have begun to provide varying levels of computing services based upon what has been referred to as a “policy based service differentiation model”.
In a policy based service differentiation model, the computing devices can offer many levels of service where different requests for different content or services which originate from different requesters receive different levels of treatment depending upon administratively defined policies. In that regard, quality of service (QoS) terms specify a guaranteed level of responsiveness minimally owed to particular content, services, or for a particular requester. The policy based service differentiation model is the logical result of several factors. Firstly, the number and variety of computing applications which generate requests across networks both private and public has increased dramatically in the last decade. Each of these applications, however, has different service requirements.
Secondly, technologies and protocols that enable the provision of different services having different levels of security and QoS have become widely available. Yet, access to these different specific services must be regulated because these specific services can consume important computing resources such as network bandwidth, memory and processing cycles. Finally, business objectives or organizational goals can be best served when discriminating between different requests rather than treating all requests for computer processing in a like manner.
As device requests flow through the network and ultimately, to a file system, storage systems provide the terminal point of data access. More particularly, in response to any data request originating in a network, a file storage device such as disk media ultimately physically retrieves the requested data. Accordingly, data caching systems at all levels of the network replicate data that ultimately can be physically retrieved from file storage. Like other elements of the network, however, In high request volume circumstances, response times attributable to file storage access can add considerable costs to the overall response time.                1. Within the modern enterprise, the enterprise can receive a substantial benefit for effectively providing differentiated service to different customers and different data so that some customers and data receive a higher level of service than other customers and data on the network. That is to say, where the enterprise satisfies the expected service level of a valued customer, the enterprise can retain the customer. Conversely, where the enterprise fails to satisfy the expected level of service of a valued customer, the enterprise likely can lose the customer. Hence, differentiated service can be an important component of e-commerce in as much as a customer always can be viewed as merely “one click away” from a competitor's system where response times falter. Yet, at present storage systems lack a means to reflect the value of data stored in a cache based upon the benefit likely to be received by the operator of the storage system when the storage system provides a particular level of differentiated service.        